1. Field of the Invention
The present invention relates to a method of boxing fuel injectors for an engine. More particularly, the present invention relates to a method of preparing a box holding a large number of fuel injectors in which a predetermined quality is secured in a predetermined number of fuel injectors forming a set for one engine.
2. Description of the Related Art
A plurality of engine parts, in this case fuel injectors, are usually used for each final assembled part, that is, engine. This plurality will be called the “first number” and this plurality of fuel injectors will be called “a set of fuel injectors”. In this case, the total value of the characteristic values of the fuel injectors forming a set sometimes has an effect on the performance of the engine.
Note that the “characteristic value” in the present specification means the performance or precision or other aspect of quality of a fuel injector. Further, the judgment as to a good part and defective part is usually made based on a management value (judgment value or threshold value) relating to the characteristic value.
As a characteristic value of a fuel injector, there is the amount of fuel leakage (fuel-tightness value). A fuel injector preferably has a fuel-tightness value of zero, but realistically a fuel injector can be used if the fuel-tightness value is slight. If the total of the fuel-tightness values of a set of fuel injectors is large, there is the danger that the lubrication oil in the engine will be diluted by the fuel and the engine bearings etc. will be damaged.
Note that in the past, the practice had been to inspect each of the fuel injectors scheduled to be mounted in an engine for that characteristic value and pack and ship out a predetermined number of only top quality parts in a single box. This “predetermined number” is a number roughly corresponding to several sets and is called a “second number”.
In the case of this boxing management, the practice had been to employ only fuel injectors with particularly small fuel-tightness values (top quality) and to strictly manage them so that the management value was satisfied even in the worst combination, but there was the problem that fuel injectors with characteristic values usable for single parts were classified as defective parts and the yield therefore became poorer.